Impairment Analytical Evaluation on Oilseed Rape Seeds Triggered by Pollen Beetle (Brassicogethes aeneus Fabricius, 1775) Especially Regarding the Fatty Acid Composition

Damage caused by Brassicogethes aeneus primarily affects the reproductive organs of rapeseed, disrupting fertilization and often leading to premature pod opening. In addition to direct yield loss, it is hypothesized that injury to generative tissues may also alter seed nutrient composition, particularly the unsaturated fatty acid profile, which is a key determinant of rapeseed quality. To assess this indirect effect, field experiments were conducted in 2024–2025, and seed samples were collected after ripening. The study aimed to evaluate pest-induced variation in nutrient content under different insecticide treatments. Alongside an untreated control, two active substances were tested: a systemic insecticide (acetamiprid) and a combined formulation of acetamiprid and lambda-cyhalothrin. Our results demonstrated that the widely used active insecticides are not effective against B. aeneus adults. Checking the fatty acid (FA) profile, within saturated FAs, the proportion of palmitic acid (C16:0) was the highest in the control; the single and combined pesticide treatments were characterized by increasing LA (C18:2n6) and ALA (C18:3n3) levels, in which both FAs exhibited a linear pattern with the single and combined treatments. In MUFAs, the most important finding was the negligible level of erucic acid (C22:1n9) below the detection limit. Oleic acid (C18:1n9) proportion was generally high (~50) and significantly decreased in treated groups. Oil quality affection highlights the importance of effective pest management to maintain the nutritional and technological value of rapeseed, as shifts in the n6:n3 ratio and thrombogenic index reflect stress responses rather than agronomic benefits.